Sound recording system



- May 22, 1934. R sc p'f 1,959,739

SOUND RECORDING SYSTEM Filed May 13, 1932 Patented May 22, 1934 UNITED STATES SOUND RECORDING SYSTEM Richard Schmidt,

assignor to Agfa Ansco Dessau in Anhalt, Germany,

Corporation, Binghamton, N. Y., a corporation of New York Application In 2 Claims.

My present invention relates to the production of sound records.

One of its objects is a device for producing photographic sound records of varying intensity, wherein sound vibrations are used to vary, by way of an electromagnetic process, the width of an exposure slit. Further objects will be seen from the detailed specification following hereafter. Reference is made to the accompanying drawing in which:

Fig. 1 is a plan view of the device according to this invention, and

Fig. 2 is an end view thereof.

Fig. 3 shows the same view as Fig. 2 but the device being provided with means to secure a constant distance of the poles a and a.

, The device consists of a magnet, between the poles a. and a of which a tongue b is arranged parallel to the limbs of the magnet. The tongue I) is fastened to a slotted square support of brass g, by means of screw 1 and. screw nut 16 and is caused to oscillate in the magnetic field by reason of electric current impulses received by the stationary coils c and 0' through which the tongue passes and which transmits these current variations to the tongue. The stationary coils c and 0 receive their current impulses by the action of the sound vibrations which are recorded by the sound receiving device (not illustrated). The tongue I) carries a blade d which faces a second blade e fixed to one of the poles of the magnet. Beneath the tongue b there are arranged the source of light I, for instance, an incandescent lamp, and a concave mirror h. By the action of the sound vibrations, the tongue b oscillates, and the exposure slit formed by the two blades 01 and e is alternately widened and narrowed. On a photographic film travelling immediately behind the exposure slit there are thus produced more or less intense latent photographic images.

If with this arrangement an expansion of the metal parts, due to the radiation of heat from the source of light, is to be feared, the magnet may be provided with compensating strips of a different metal or the whole device may be fixed on a rigid frame preventing any expansion.

On account of the heat radiation of the glow lamp the magnet may be so strongly heated that it is somewhat bent open whereby the slit between the blades d and e may be unduly enlarged. In order to prevent this drawback the poles at and a may be united to a rigid frame by means of an unmagnetizable material, for instance, brass. Such an arrangement is shown in Fig. 3 wherein the poles a and a are on both sides surrounded by blocks 11. of brass united with the same to a rigid frame by means of screws s and screw nuts 1. In another arrangement the magnet is given on its inner side a support m (cf. Fig. 1) of a material May-13, 1932, Serial No. 611,185 Germany May 19, 1931 having a low expansibility, for instance, a nickel steel containing about 36 per cent of nickel, the so-called invar, the expansibility of which amounts to less than 1 per cent of that of iron. In the case of heating an increased bent is produced which by suitably selecting the support of invar just compensates the undesired change of form.

The slit can be protected from dust by extending over the blades an elastic transparent membrane of any colloidal material, for instance, a film of a cellulose derivative or of regenerated cellulose, or by arranging over the blades a very thin lamina of glass, quartz or the like. The covering must. of course, be arranged in a way that it does not hinder the oscillation of the blade fixed to the tongue I). In Fig. 1, for instance, the elastic membrane 1 covers the blades d, e. It is pasted to the blade at and the limb a of the magnet, the distance between the places of attachment to the blade and the limb being sufliciently great so that the oscillation of the blades is not hindered.

The device presents the considerable advantage of being highly sensitive so that it is even possible to produce the record without the usual amplification by tubes. It is, of course, possible to combine the device with the known amplifying tubes, if desired.

What I claim is:

1. A device for producing photographic sound records of varying intensity which comprises a magnet having two limbs, one of said limbs being provided with a blade, a tongue arranged between and parallel to said limbs and provided with a blade forming a slit with said blade of said magnet, said tongue being provided with stationary field coils causing said tongue to oscillate on electric impulses communicated to said coils, and a source of light arranged between the limbs of said magnet.

2. A device for producing photographic sound records of varying intensity which comprises a magnet having two limbs, one of said limbs being provided with a blade, a tongue arranged between and parallel to said limbs and provided with a blade forming a slit with said blade of said magnet, said tongue being provided with stationary field coils causing said tongue to oscillate on electric impulses communicated to said coils, and a source of light and a concave mirror being arranged between the limbs of said magnet, said mirror being arranged behind said source of light, remote from said slit.

RICHARD SCHMIDT. 

